MgO insertion into free layer for magnetic memory applications

Patent metadata

Field	Value
Publication number	US-10193062-B2
Application number	US-201815972284-A
Country	US
Kind code	B2
Filing date	May 7, 2018
Priority date	Mar 17, 2017
Publication date	Jan 29, 2019
Grant date	Jan 29, 2019

Abstract

A magnetic tunnel junction (MTJ) is disclosed wherein first and second interfaces of a free layer (FL) with a first metal oxide (Hk enhancing layer) and second metal oxide (tunnel barrier), respectively, produce perpendicular magnetic anisotropy (PMA) to increase thermal stability. In some embodiments, a continuous or discontinuous metal (M) or MQ alloy layer within the FL reacts with scavenged oxygen to form a partially oxidized metal or alloy layer that enhances PMA and maintains acceptable RA. M is one of Mg, Al, B, Ca, Ba, Sr, Ta, Si, Mn, Ti, Zr, or Hf, and Q is a transition metal, B, C, or Al. Methods are also provided for forming composite free layers where interfacial perpendicular anisotropy is generated therein by contact of the free layer with oxidized materials.

First claim

We claim:

1. A magnetic element, comprising:
(a) a tunnel barrier layer that is a first metal oxide layer;
(b) a Hk enhancing layer or a non-magnetic metal or alloy layer (NML); and
(c) a composite free layer having a stack of layers in a FL 1 /M/FL 2 or FL 1 /MQ/FL 2 configuration where the FL 1 and the FL 2 are free layers and wherein a first free layer (FL 1 ) forms a first interface with the tunnel barrier layer, a second free layer forms a second interface with the Hk enhancing layer or NML, and M and MQ are a metal and metal alloy layer, respectively, that are partially oxidized to a non-stoichiometric oxidation state by scavenging oxygen during formation of the magnetic element thereby enhancing perpendicular magnetic anisotropy (PMA) in the composite free layer.

2. The magnetic element of claim 1 wherein M is an element selected from Mg, Al, B, Ca, Ba, Sr, Ta, Si, Mn, Ti, Zr, and Hf, Q is unequal to M, and Q is an element that B, C, Al, or a transition metal.

3. The magnetic element of claim 1 wherein the second free layer is the FL 2 , and the FL 1 and the FL 2 are comprised of one or more of Co, Fe, CoFe, CoFeB, CoB, FeB, CoFeNi, and CoFeNiB, or a high Ku material having inherent PMA which is a Heusler alloy that is Ni 2 MnZ, Pd 2 MnZ, Co 2 MnZ, Fe 2 MnZ, Co 2 FeZ, Mn 3 Ge, or Mn 2 Ga where Z is one of Si, Ge, Al, Ga, In, Sn, and Sb, or an ordered L 1 0 or L 1 1 material with a composition that is one of MnAl, MnGa, and RT wherein R is Rh, Pd, Pt, Ir, or an alloy thereof, and T is Fe, Co, Ni, or an alloy thereof, or a rare-earth alloy with a TbFeCo, GdCoFe, FeNdB, or SmCo composition.

4. The magnetic element of claim 1 wherein the composite free layer is further comprised of a second metal layer (M 2 ) or second metal alloy layer (M 2 Q 2 ) adjoining the FL 2 layer, and a third free layer (FL 3 ) contacting the second metal layer or second metal alloy layer to give a FL 1 /M/FL 2 /M 2 /FL 3 , FL 1 /M/FL 2 /M 2 Q 2 /FL 3 , FL 1 /MQ/FL 2 /M 2 Q 2 /FL 3 , or FL 1 /MQ/FL 2 /M 2 /FL 3 configuration where M 2 is one of the M elements, and Q 2 is one of the Q elements.

5. The magnetic element of claim 4 wherein the second free layer that forms the second interface with the Hk enhancing layer or NML layer is the FL 3 .

6. The magnetic element of claim 4 wherein the FL 3 is comprised of one or more of Co, Fe, CoFe, CoFeB, CoB, FeB, CoFeNi, and CoFeNiB, or a Heusler alloy that is Ni 2 MnZ, Pd 2 MnZ, Co 2 MnZ, Fe 2 MnZ, Co 2 FeZ, Mn 3 Ge, or Mn 2 Ga where Z is one of Si, Ge, Al, Ga, In, Sn, and Sb, or an ordered L 1 0 or L 1 1 material with a composition that is one of MnAl, MnGa, or RT wherein R is Rh, Pd, Pt, Ir, or an alloy thereof, and T is Fe, Co, Ni or an alloy thereof, or a rare-earth alloy with a TbFeCo, GdCoFe, FeNdB, or SmCo composition.

7. The magnetic element of claim 4 wherein the Hk enhancing layer or the NML forms the second interface with the second free layer, and further comprising a seed layer formed on a substrate, a reference layer (RL) on the seed layer, and an uppermost capping layer to yield a seed layer/RL/tunnel barrier layer/composite free layer/Hk enhancing layer/capping layer configuration, or a seed layer/RL/tunnel barrier layer/composite free layer/NML/capping layer configuration.

8. The magnetic element of claim 4 wherein the Hk enhancing layer or NML forms the second interface with the second free layer, and further comprising a seed layer formed on a substrate, a reference layer (RL) on the tunnel barrier layer, and a capping layer on the RL to yield a seed layer/Hk enhancing layer/composite free layer/tunnel barrier layer/RL/capping layer configuration, or a seed layer/NML/composite free layer/tunnel barrier layer/RL/capping layer configuration.

9. The magnetic element of claim 4 wherein the composite free layer is further comprised of a third metal layer having a M 3 or M 3 Q 3 alloy composition formed on the FL 3 layer, and a fourth free layer (FL 4 ) formed on the third metal layer where M 3 is one of the M elements, and Q 3 is one of the Q elements.

10. The magnetic element of claim 9 wherein the composite free layer is further comprised of a fourth metal layer having a M 4 or M 4 Q 4 alloy composition formed on the FL 4 layer, and a fifth free layer (FL 5 ) formed on the fourth metal layer where M 4 is one of the M elements, and Q 4 is one of the Q elements.

11. The magnetic element of claim 10 wherein each of the FL 4 and the FL 5 is comprised of one or more of Co, Fe, CoFe, CoFeB, CoB, FeB, CoFeNi, and CoFeNiB, or a Heusler alloy that is Ni 2 MnZ, Pd 2 MnZ, Co 2 MnZ, Fe 2 MnZ, Co 2 FeZ, Mn 3 Ge, or Mn 2 Ga where Z is one of Si, Ge, Al, Ga, In, Sn, and Sb, or an ordered L 1 0 or L 1 1 material with a composition that is one of MnAl, MnGa, or RT wherein R is Rh, Pd, Pt, Ir, or an alloy thereof, and T is Fe, Co, Ni or an alloy thereof, or a rare-earth alloy with a TbFeCo, GdCoFe, FeNdB, or SmCo composition.

12. The magnetic element of claim 1 wherein the Hk enhancing layer or the NML forms the second interface with the second free layer, and further comprising a seed layer formed on a substrate, a reference layer (RL) on the seed layer, and an uppermost capping layer to yield a seed layer/RL/tunnel barrier layer/composite free layer/Hk enhancing layer/capping layer configuration, or a seed layer/RL/ tunnel barrier layer/composite free layer/NML/capping layer configuration.

13. The magnetic element of claim 1 wherein the Hk enhancing layer or the NML forms the second interface with the second free layer, and further comprising a seed layer formed on a substrate, a reference layer (RL) on the tunnel barrier layer, and a capping layer on the RL to yield a seed layer/Hk enhancing layer/composite free layer/tunnel barrier layer/RL/capping layer configuration, or a seed layer/NML/composite free layer/tunnel barrier layer/RL/capping layer configuration.

14. A method of forming a magnetic element exhibiting interfacial perpendicular anisotropy at a first interface between a free layer and a first oxide layer, and at a plurality of interfaces where the free layer contacts a plurality of metal oxide clusters formed within the free layer, comprising:
(a) providing the first oxide layer or a first non-magnetic metal or alloy (NM 1 ) layer on a substrate;
(b) depositing the free layer (FL) with a plurality of metal clusters therein on the first oxide layer or on the NM 1 layer;
(c) depositing a second oxide layer or a second non-magnetic metal or alloy (NM 2 ) layer on a top surface of the free layer that faces away from the first oxide layer or the NM 1 layer; and
(d) performing an annealing step such that during one or more of steps (b), (c), and (d), the plurality of metal clusters scavenge oxygen from one or more layers in the magnetic element, and react with the scavenged oxygen to form a plurality of metal oxide clusters that interface with portions of the free layer thereby enhancing perpendicular magnetic anisotropy (PMA) therein.

15. The method of claim 14 wherein the free layer has a thickness from about 5 to 15 Angstroms.

16. The method of claim 14 wherein the plurality of metal oxide clusters has a stoichiometric or a non-stoichiometric oxidation state.

17. The method of claim 14 wherein the free layer is a single layer or multilayer of one or more of Co, Fe, CoFe, CoFeB, CoB, FeB, CoFeNi, and CoFeNiB.

18. The method of claim 14 wherein the free layer is comprised of a high Ku material having inherent PMA which is a Heusler alloy that is Ni 2 MnZ, Pd 2 MnZ, Co 2 MnZ, Fe 2 MnZ

Assignees

• Headway Tech Inc

Inventors

• IWATA Jodi Mari
• Jan Guenole
• Tong Ru-Ying
• Wang Po-Kang

Classifications

• H01F10/16

  containing cobalt ({H01F10/126} , H01F10/13 take precedence) · CPC title

• H01F41/32

  for applying conductive, insulating or magnetic material on a magnetic film {, specially adapted for a thin magnetic film} · CPC title

• H01F10/3254

  the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ] · CPC title

• G11C11/161

  details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell · CPC title

• H01F10/32

  Spin-exchange-coupled multilayers, e.g. nanostructured superlattices {(applying spin-exchange-coupled multilayers to substrates H01F41/302)} · CPC title